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[24.9.77.57]) by smtp.googlemail.com with ESMTPSA id f8sm1435548ioc.24.2020.11.25.11.37.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Nov 2020 11:37:20 -0800 (PST) From: Jim Cromie To: linux-mm@kvack.org Cc: gregkh@linuxfoundation.org, linux@rasmusvillemoes.dk, Jim Cromie , Jason Baron , linux-kernel@vger.kernel.org Subject: [PATCH 2/7] dyndbg: count repetition in __dyndbg_callsite fields. Date: Wed, 25 Nov 2020 12:36:21 -0700 Message-Id: <20201125193626.2266995-3-jim.cromie@gmail.com> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20201125193626.2266995-1-jim.cromie@gmail.com> References: <20201125193626.2266995-1-jim.cromie@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: The __dyndbg_callsite section is basically a flat db-table, an array of struct _ddebug_callsite[]s. Its data is inherently hierarchical and sorted, so a field-wise run-length encoding would compress well. Add counters and code to test 3 fields of consecutive callsites for repeated values. The results inform a compression estimate. dyndbg: 2605 entries. repeated entries: 2369 module 2231 file 1147 func Thats (91%, 86%, 44%) repeated values in those pointers/columns, on my i7 laptop build. With a zero-overhead markup, like LSB-stealing, we could mark the differing tails of consecutive records, and get 11/24 compression on init/main pr_debugs. For a slightly apples-to-oranges comparison (text vs pointers), `gzip /proc/dynamic_debug/control` achieves 6/1 compression. Signed-off-by: Jim Cromie --- lib/dynamic_debug.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c index 2e4a39c349a5..5980d44ff2f8 100644 --- a/lib/dynamic_debug.c +++ b/lib/dynamic_debug.c @@ -1081,11 +1081,12 @@ static int __init dynamic_debug_init_control(void= ) =20 static int __init dynamic_debug_init(void) { - struct _ddebug *iter, *iter_start; + struct _ddebug *iter, *iter_start, *prev =3D NULL; const char *modname =3D NULL; char *cmdline; int ret =3D 0; int n =3D 0, entries =3D 0, modct =3D 0; + int modreps =3D 0, funcreps =3D 0, filereps =3D 0; =20 if (&__start___dyndbg =3D=3D &__stop___dyndbg) { if (IS_ENABLED(CONFIG_DYNAMIC_DEBUG)) { @@ -1099,7 +1100,16 @@ static int __init dynamic_debug_init(void) iter =3D __start___dyndbg; modname =3D iter->site->modname; iter_start =3D iter; - for (; iter < __stop___dyndbg; iter++) { + for (prev =3D iter; iter < __stop___dyndbg; iter++) { + if (entries) { + if (prev->site->modname =3D=3D iter->site->modname) + modreps++; + if (prev->site->function =3D=3D iter->site->function) + funcreps++; + if (prev->site->filename =3D=3D iter->site->filename) + filereps++; + prev++; /* one behind iter */ + } entries++; if (strcmp(modname, iter->site->modname)) { modct++; @@ -1122,6 +1132,9 @@ static int __init dynamic_debug_init(void) (int)(entries * sizeof(struct _ddebug)), (int)(entries * sizeof(struct _ddebug_callsite))); =20 + vpr_info("%d entries. repeated entries: %d module %d file %d func\n", + entries, modreps, filereps, funcreps); + /* apply ddebug_query boot param, dont unload tables on err */ if (ddebug_setup_string[0] !=3D '\0') { pr_warn("ddebug_query param name is deprecated, change it to dyndbg\n"= ); --=20 2.28.0